1. Field of the Invention
The present invention generally relates to a thin film fabrication of a rubber material with piezoelectric characteristics and a manufacturing method thereof, more particularly to a thin film fabrication that is developed by utilizing polymer casting, multilayer stacking, surface coating, and micro plasma discharge processes.
2. Description of the Prior Art
In prior arts, to produce the desired cellular structures, most ferroelectrets are formed utilizing a modified film blow and extrusion process. Before film blowing, spherical voids with diameters about 10 μm are generated by gas injection into the polymer melt. The melt is extruded into a tube which is cooled down and reheated for film blowing. Film formation is accompanied by biaxial orientation, which results in disk- or lens-shaped voids. Unfortunately, the results are usually ill-controlled in both individual void geometry and overall cellular structure, owing to the polydispersity resulting from the fabrication processes. It is difficult to control the cellular structures and therefore the properties of the fabricated ferroelectrets, or to further integrate them with common microsystems.
A US patent, numbered U.S. Pat. No. 8,217,381 and called Controlled Buckling Structures in Semiconductor Interconnects and Nanomembranes for Stretchable Electronics, discloses the technology listed below:                the present invention provides stretchable, and optionally printable, components such as semiconductors and electronic circuits capable of providing good performance when stretched, compressed, flexed or otherwise deformed, and related methods of making or tuning such stretchable components. Stretchable semiconductors and electronic circuits preferred for some applications are flexible, in addition to being stretchable, and thus are capable of significant elongation, flexing, bending or other deformation along one or more axes. Further, stretchable semiconductors and electronic circuits of the present invention are adapted to a wide range of device configurations to provide fully flexible electronic and optoelectronic devices.        
With references to FIG. 8A and FIG. 8C, FIG. 8B and FIG. 8D, which illustrate a schematic view of a method for fabricating a smooth wavy elastomer substrate of U.S. Pat. No. 8,217,381 and a schematic structural view of each step of the method for fabricating a smooth wavy elastomer substrate of U.S. Pat. No. 8,217,381. As shown in figures, Anisotropic Si 100 etching provides a substrate 20 having sharp-edges 24, as shown in FIG. 8B. Spin PR smoothes the sharp-edged valleys by depositing PR 26 in the sharp-edged valleys 24 of substrate 20. An elastomeric stamp 34 is cast against substrate 20. Stamp 34 has sharpedged recess features. A second elastomeric stamp 36 is cast on stamp 34 to generate a stamp having sharp-edged peaks. Stamp 36 is embossed with Su-8 50 and cured as appropriate. Spin PR 26 smoothes the sharp-edged valleys of 50. Elastomeric substrate 30 is cast against the 50 having smooth valleys. Substrate 30 is removed to reveal a wavy and smooth surface 32. Further, the independent claim of U.S. Pat. No. 8,217,381 is as below:                A two-dimensional stretchable and bendable device comprising: an elastomeric substrate having a contact surface; an interconnect having a first end bonded to said elastomeric substrate contact surface and a second end bonded to said elastomeric substrate contact surface, and a central portion between said first and second ends; wherein movement of said first end and said second ends toward each other generates a curve and physical separation between said elastomeric substrate contact surface and interconnect central portion with a maximum physical separation distance between said central portion and said elastomeric substrate contact surface that is greater than or equal to 100 nm and less than or equal to 1 mm; said first end connected to a first contact pad and said second end connected to a second contact pad, wherein said contact pads are substantially flat for receiving a device component and said contact pads are bonded to said substrate; wherein said interconnect electrically connects said first contact pad and said second contact pad, and said curved central portion provides said device stretching and bending while maintaining electrical connectivity when said contact pads move relative to one another.        
For the aspect of functions of U.S. Pat. No. 8,217,381, it discloses how a smooth wavy elastomer substrate and a two-dimensional stretchable and bendable device are fabricated. It is not enough to develop a thin film fabrication of a rubber material with piezoelectric characteristics through utilizing polymer casting, multilayer stacking, surface coating, and micro plasma discharge processes. Hence to design the thin film fabrication of the rubber material with the piezoelectric characteristics is an important issue for the people skilled in the art.